Nested pseudo-selectors that take selectors eport missing a closing ')' when separated by commas

[matthew-dean]

To reproduce:

a:is(.b, :is(.c)) {
  color: blue;
}

Current behavior:

Reports Missing closing ')' even though parentheses are balanced. This is true for :is(), :where(), and :not() which all can accept selector lists, meaning those selector lists may also have :is(), :where(), and :not(). It's possible that those pseudo-selectors are not parsing their contents as selectors.

Expected behavior:

Selectors should support nesting of selectors within pseudo-selectors that take relative selector lists as input

Environment information:

• less version: 4.2.0
• nodejs version: Current Less preview
• operating system: